I guess I missed this, lol...What species of parrot is Max? I skimmed through here but didn't see it mentioned, only that he is 3 years-old. Also, was Max ever DNA-tested for gender, or are you only assuming he's a boy? It does make quite a large difference with regard to hormonal behavior, that's why I ask. Also, were you his first owner? Was he hand-raised and tame/able to be handled when you first brought him home? Did he used to interact with you differently before this sudden change last spring? And as far as the "dog incident" and what time period that occurred with relation to when Max's personality changed, which came first?
I appreciate that you boarded him at an Aviary and they gave him a "health check", but whenever a sudden and dramatic behavioral/personality change occurs in a bird, the very first thing that needs to be done is a complete "Wellness-Exam" by either a Certified Avian Vet or an Avian Specialist Vet (no "Exotics Vets"), and this Wellness-Exam needs to include a Fecal Culture and Microscopy/Gram-Stain, and even more importantly it needs to include routine Blood-Work (especially if Max has never had baseline Blood-Work done ever before). Captive/Pet parrots should have a full Wellness-Exam that includes the basics (Fecal and baseline Blood-Work) once a year at the least, so that you have comparison blood values for when something like this happens...Also, what were the specific injuries that Max obtained from the dog-attack? This could be very important to specifically look at, because it's very common for permanent nerve damage to be the cause of chronic/constant pain, and it's very likely that Max did retain some permanent nerve damage from the dog bites/injuries. This could very well be the cause of his personality change, and the only way to really figure this out is to have a CAV prescribe Max some pain-medication/anti-inflammatory medication and see if his personality changes at all for the better while he's on the pain-meds. This isn't at all unusual to try, the same thing is often first tried with parrots who suddenly start plucking, they are put on a pain-medication and if the plucking stops while on the pain medication but then starts again once the pain medication is stopped, then they know that the bird is plucking due to physical pain and not a psychological/mental issue. And physical problems such as constant pain/discomfort/itching are much easier to treat then most psychological/mental issues in birds, such as depression. So you should also discuss with the CAV the possibility of prescribing Max a mild pain-killer, such as Tramadol, or a very effective anti-inflammatory, such as Metacam, for a trial-period to see if this changes his personality/behavior back to the way he used to be. If so, then you have your answer and can move forward from there, but at least you can stop the pain he would have been in since the Spring. Unfortunately they can't just tell us "Daddy I hurt" or "Mommy I'm itchy all the time", so it's necessary that we assume they are in pain/discomfort of some kind when they are acting differently than they usually are, because obviously the first thing we need to do is stop their pain...And with a dog-attack like Max endured, it's not unusual for them to suffer injuries that we can't see on an X-Ray, such as nerve damage, subtle spinal injuries, etc.
The big deal with having a CAV do a Fecal and routine Blood-Work is because obviously we all know that all birds possess an innate, natural instinct to hide any and all outward signs of illness and pain for as long as they possibly can, as a survival instinct. Usually by the time we as peope notice that something is wrong with our birds, they have been sick for a long, long time, often months and months...Something that is often forgotten or not spoken about is that sometimes when birds are purposely hiding outward signs/symptoms of illness and/or pain, it comes-out as a personality or behavioral change, rather than a clear sign/symptom of illness or pain, such as lethargy, loss of appetite, constantly being fluffed-up, etc. So it is quite possible that Max is suffering from some type of illness/infection/disease, or residual pain from a past injury, that is being expressed as a personality/behavioral change. The only way to know for sure is to have routine, baseline Blood-Work done to look for infection, anemia, liver function, kidney function,
nutritional deficiencies, etc., and then to also check his GI Tract for Fungi (yeast), negative Bacteria, a lack of healthy, normal Bacteria, etc. You said his behavioral/personality change started suddenly, out of nowhere, and just this past spring, so that timeline is not at all out of line with some physical cause at this point. It's quite possible that Max is in some type of constant/chronic pain, discomfort, itching, etc., and this is why he suddenly started distancing himself from you/people,
not wanting to be touched, handled, or generally "bothered" because he doesn't feel well or due to pain/discomfort. Routine Blood-Work is easy, non-invasive, inexpensive, and should be done once a year anyway, so even if they find nothing wrong physically with Max, you'll have normal, baseline blood-work for future comparison, and you'll also get the overall-picture of his liver and kidney functions, how his diet is treating his body, etc.
This should always be the very first thing you do whenever your bird starts behaving/acting differently or has a sudden personality change that doesn't correct itself, simply due to the innate survival-instincts that all birds possess, and the fact that it's not unusual for them to hide pain/discomfort/constant itching, etc. for months and months to well over a year. Just think about how we would be acting if we were in constant, steady pain, discomfort, itching, etc. We wouldn't want to be touched or bothered by anyone either...
***If the Fecal Culture and Blood-Work show nothing physically causing Max's personality/behavioral change, or if you try putting him on a pain-medication for a short period of time (Metacam would be the drug of choice because it's both a pain medication and an anti-inflammatory), then you have to assume it was some type of environmental issue/change that caused it...Since the change in Max's behavior and personality was so sudden and out of nowhere last Spring, and has continued since then, try to think back to right around that time, specifically the month that this change started, and try to remember if there were any changes to/in your home or with the people who live in your home. I know it's hard to remember every little detail that happened last Spring, but with birds even very tiny changes to their environment, their diet, their regular, daily routine, or with/within their "Flock" can cause exactly what has been going on with Max. Little, tiny changes that we as people would think of as being totally insignificant can totally up-end a parrot's world and cause this type of sudden personality change...So any changes that may have occurred to especially his cage, his stands, his toys, or any of his "territory" would be the first thing to think about, or a change of the location of his cage/stands etc. Then move-on to his daily diet, did you change food brands or types? Did you change the types of veggies/fruit he normally gets? Then move on to your household dynamic...Did anyone move-out, did anyone move-in, did you start using different cleaners, detergents, etc. in your house around that time, etc. Then how about to your personal schedule (I'm assuming you were/are Max's "person" in the house)...Did you change your work-schedule, did the normal time you spent with Max change, did you start spending less time at home, did you bring anyone new into Max's life (meaning into your life), etc. Did you add any new pets to your home? For example, even if you don't see the dog bothering Max, meaning the dog doesn't pay any attention to Max and Max doesn't pay any attention to the dog, that doesn't in any way mean that the dog isn't Max's issue. Parrots have the intelligence of a 3-4 year-old human child, and they possess the ability to reason and use logic. They are also extremely emotionally-driven,
just like people are. So just because the dog and Max don't outwardly "pay any attention to each other", that doesn't at all mean that the dog isn't the issue for Max. Think about it in-terms of how we as people behave when something is bothering us. We often hide our true feelings about something for a long, long time, yet the people around us and close to us know that something is bothering us, just because they notice we are acting differently than normal. However, even though our loved ones know something is bothering us/wrong with us, they often have no idea what, and when we finally decide to break-down and tell them what it is that has been bothering us, they are often very surprised and would have never guessed that the source of our problem is what it is...The same goes for parrots, and emotions such as jealousy, envy, and the need for dominance and to be at the top of the pecking-order in their home and among their "Flock" often drives their behavior and forms their outward personality. This is why parrots often start plucking, self-mutilating, biting, attacking, etc. whenever a new pet or person is brought into their "Flock", because they are viewed as competition.